Die units of this type have hitherto been set up, without exception, by a fully profiled forming die being produced over its entire length with its stamping cross section being cut out from a solid hardened block over its entire length by wire erosion. In a conventional method for fastening the die in the die-holding plate, an embossing die is produced in the form of the die, with the peripheral chamfer which is desired. The upper end of the forming die is subsequently heated and the chamfer is upset on the die by means of a press in the embossing mould. The chamfer of the upset head also serves for withdrawing the stamping die, the heating described bringing about the additional effect that the hardness of the die is reduced in the head region due to the annealing effect.
After the forming die has been pushed into the die receptacle, the latter is ground over on the head side and then screwed to a pressure plate made from hardened steel. During a stamping stroke, the stamping forces then act via the pressure plate upon the die head which forms the rear end of the forming die.
This solution makes it necessary for a dedicated die unit to have to be kept ready for every stamping-die cross section required, wherein the die-holding plate has to be manufactured individually for each individual forming die.
A die unit produced in this way is fastened to an upper part of a stamping tool, for example by means of two screws, this mostly being a column-guided standard frame. A plurality of individual die units may be installed in a tool if a plurality of desired perforations are to be made.